This invention relates to shackles and more particularly to handcuffs, and leg irons, with double-locking mechanisms.
Handcuffs, such as those shown in U.S. Pat. No. 2,390,885 to Kelley, typically have a pair of arcuate frame parts, known as a jaw and cheek, that are pivotally coupled to one another. A pawl-and-ratchet mechanism permits one-way rotational movement of the jaw as it pivots through the spaced apart arms or plates that form the cheek. Teeth on the pawl's underside ride over complimentary ratchet teeth in the top of the jaw, as the jaw rotates into the cheek, to lock the cuff around a person's wrist. Spring pressure atop the pawl is meant to prevent the jaw from backing off and unlocking the cuff.
As described in the aforementioned patent to Kelley (assigned to the Peerless Handcuff Company), skilled lock pickers could open old-fashioned cuffs by lifting the pawl and sliding out the unencumbered jaw. Kelley therefore added a slide bolt that overlay the pawl, inside the frame. When a tiny key end (element No. 9 in Kelley's drawings) was pushed into a side channel of the frame, a separate drift pin (carried in the channel) moved against an end of the bolt. Continued pressure caused the bolt to slide so that an interference surface on it would then abut the pawl. This surface blocked the pawl to prevent it from being lifted; and it would hopefully remain in place until the authorized user inserted the key's other, main end to unlock the cuff.
This "slide-bolt" assembly acted as a "double lock". Not only did the bolt prevent the jaw from being picked open, it also acted to prevent overtightening of the cuff. Overtightening used to occur after a jaw and cheek were initially coupled properly about a wearer's wrist. If the outside of the cuff's jaw was accidentally struck, it could pivot further under the pawl. The result was often painful, and cut off blood flow in the wearer's hand. But, with the bolt, the pawl could be kept in place, so that the jaw could not move in either rotational direction.
While Kelley's slide bolt assembly was an improvement, its bolt sometimes slipped into place prematurely. That would block the cuff's jaw and cheek from locking together initially. That type of flaw is exasperating to police, who rightfully expect a cuff to operate. They do not want to fumble with a cuff when they are trying to subdue a dangerous felon.
Slide bolts have therefore been modified, such as to that disclosed in U.S. Pat. No. 4,509,346 to Szczepanek, assigned to Universal Tool Company, Inc. That patented structure is shown as "Prior Art" in this application's FIG. 2. As described in the Abstract of Szczepanek's patent. "The unintentional movement of the bolt into its double-locking position is prevented by providing a restraining means--a spring loaded pin [element No. 27 in the patent's drawings]--that operates against the casing and the bolt to resiliently urge the bolt against the latch and against the spreading of the action of mating shoulders [24, 25] on the bolt and latch that cause the two to spread apart against the action of the restraining means as the bolt moves forward toward the double-locking position and the shoulders engage." While the patent purports that this structure also prevents unintentional dislodging of the bolt from its locking position, it is relatively ineffective in that regard. By smashing the side of the cuff against a hard surface, the slide bolt can become dislodged, whereupon it automatically retracts to its original position, due to the spring force caused by the spring 27 adjacent the drift pin.
There is also another drawback with prior slide-bolt assemblies: They utilize a separate drift pin, like the one shown in Szczepanek, to push the slide bolt into its double-locking position. Sometimes, the pin seizes or breaks. A user is then frustrated because the assembly does not work.
It is therefore a primary object of the present invention to provide an improved double-locking mechanism for handcuffs (and leg irons) that overcomes the problems of the prior art.
It is another general object to provide an improved double-locking mechanism that avoids premature actuation or dislodging.
It is still another object to provide such a double-locking mechanism, with a unitary slide bolt, that is less susceptible to failure or breakage.
It is a further object to provide an improved double-locking mechanism that is constructed to afford increased strength and more reliability in the field.